If you’re getting tired of reading about SIDs, then you’re not alone. As important as they are, it’s just difficult to make interesting reading from them. However, a good understanding of these weak points in our Cessna’s structure is the only thing that will allow us the ability to keep them flying safely for the foreseeable future.

SID 53-47-01 Seat Rails and Corrosion Inspection

Type of Inspection – Visual

Initial Compliance: 5 years

Recurring Compliance: 5 years

Approximate Labor Time – 1 hour

One might view this as part of the crew seat latching system Airworthiness Directive, but it is a different inspection. It is important to understand that the seat rails are a significant part of the floor structure. Even if no seat were installed, the rails must be in proper condition for complete structural continuity.

I remember my college days working as a ticket agent for Air Illinois, a commuter airline flying several types of turboprops and a couple of jets. The ticket agents were responsible for the loading manifest which used “standard” weights for passengers and baggage. The “standard” male passenger in 1979 weighed 170 pounds and a bag was 24 pounds. We even used slightly higher weights for winter months. The current standard male weight is well past 180.

The point is that as we (Americans) get heavier, we’re adding significant stress to the seat rails. That stress is also transferred to the structure under the floor. All that heavy flexing of the floor deserves a little special attention from time to time. This SID is another of those obvious inspections that Cessna savvy mechanics have been doing for years.

SID 55-10-01 Horizontal Stabilizer, Elevators, and Attachment Inspections

SID 55-30-01 Vertical Stabilizer, Rudder, and Attachment Inspections

Type of Inspection – Visual with Eddy Current if needed

Initial Compliance: 5000 hours or 20 years

Recurring Compliance: 2000 hours or 5 years

Approximate Labor Time – 2 hours

I’ve grouped these two SIDs together as Cessna suggests in the documents. They are basically the same inspection except one is horizontal and the other vertical.

There’s nothing special in this inspection except to make it much more detailed than usual. This is a “look in every nook and cranny” type of inspection. The elevator and rudder bearings are part of it as well.

I would add a personal pet peeve of mine that is very often missed or ignored during the typical annual inspection. While the center area of the horizontal stabilizer is open, one should be certain to inspect and lubricate the two small elevator trim pulleys mounted there. The cables make a very sharp 90 degree turn here which creates significant friction between the strands and should be lubricated too.

 

SID 57-11-01 Wing Structure Inspection

Coordinate with SID 57-40-01 Strut and Strut Wing Attachment Inspection

Type of Inspection – Visual with possible Eddy Current

Initial Compliance: 6000 hous or 10 years

Recurring Compliance: 1000 or 5 years

Approximate Labor Time – 8 hours plus extra for Eddy Current

These visual inspections call for use of a borescope where needed. That should be an indicator to the inspector about the intense level of detail required for this inspection.

These two SIDs deal with some of the most intense structural attachments on the plane. It may come as a surprise to some of you that there is only one bolt at each end of the lift strut. If either bolt fails, the wing attach bolts become very effective hinge points. The wing will freely move up and down pivoting on the wing attach bolts. If this should happen in flight, the wing will easily fold straight up. I’m not trying to scare anyone, just instilling the practicality (prudence) of doing this inspection.

This is not something that’s a part of any routine annual inspection and so will be a significant extra effort.

Removing the wing attach bolts sounds pretty invasive at first, but it’s far less risky than R&R of an engine cylinder. I say that because the likely errors made during wing R&R are more difficult to make and much easier to detect than those made during cylinder work. Mostly, as long as one remembers to reinstall the bolt with the locking nut, all is well. They are very large bolts by small airplane standards, but they don’t need much torque. This is because they are loaded almost exclusively in shear, so the main purpose of the nut is to just keep the bolt in place.

If it is determined to pull all the bolts that support the wing, one at a time is a good policy. This helps prevent putting stress on fuel lines and control cables should the wing move out of position. Removing the lift strut from the wing will require raising the wing tip about a foot. It works well to have a ladder with a foam pad on top to rest the outboard wing. You’ll also want to support the lift strut or it will drop to the floor. This isn’t a terrible problem if you have a model where the strut is attached externally at the fuselage end, but will do some structural skin damage if it’s mounted inside the cabin.

Sometimes the attach bolts are very difficult to remove. Often a large hammer and a  brass drift punch will be involved in their removal.

Hammers and airplanes are a strange combination but get along OK if you follow a little common sense. If you have to drive a bolt out and expect to reuse it, the threads will need to be protected during the process. It works well to back the nut off until only a few threads are still engaged with the bolt. The nut is a good sacrificial part so one can whale away on the old one without damaging the bolt. Replacement nuts are cheap and should probably be replaced anyway.

Bolts are steel and susceptible to rust so following the lubrication recommendations in the service manual is highly recommended. Also, check the torque values in the manual for proper torqueing of the nut and whether the threads should be dry or lubricated. I could tell you whether dry threads or wet but maybe the intrigue will make you actually check out the service manual.

SID 57-11-02 Wing Structure Corrosion Inspection

Type of Inspection – Visual

Initial Compliance: 10 years

Recurring Compliance: 5 years

Approximate Labor Time – 6 hours

Four hours may seem like a lot of time just to inspect the inside of the wings, but there’s more to it than you might think. By the time ALL the access panels, wing tip, and fuel tank panels are removed, you’ve eaten up a good part of the first hour (rusted screws and such). Then using a borescope to get into every corner, every rivet, every string, etc. adds to the process. Oh, don’t forget you have to reinstall all those panels and replace the screws that you had to drill.

SID 57-11-04 Wing Splice Joint and Strut Attach Inspection

Type of Inspection – Visual, ultrasonic if needed

Initial Compliance: 10 years

Recurring Compliance: 5 years

Approximate Labor Time – 2 hours

The forward wing spar is spliced in the same place as the wing lift strut attachment. There are several layers of parts here which were not corrosion protected in the original production. This make it very susceptible to corrosion between the parts. If any deformation of the splice plates or spar webs is noted visually, an ultrasonic test is the only practical means to determine the extent of the damage.

The wing spar splice point is a significant stress point. The lift stress outboard of the splice converge with the bending and twisting moments at the splice and the lift strut attachment. If there’s a problem in this area, you really want to know about it.

The spar splice is in the same area as the lift strut attachment. I would recommend doing this inspection at the same time as the 57-40- 01 to combine some of the labor.

SID 57-12-01 Wing Root Rib Corrosion Inspection

Type of Inspection – Visual

Initial Compliance: 3 years

Recurring Compliance: 3 years

Approximate Labor Time – 3 hours

Again, access is the key to getting this inspection done. There are plenty of points on the outboard side of the wing root rib that may be difficult to see. Corrosion in this area is accelerated by the moisture from the cabin air ducts that often leak.

 SID 57-51-01 Aileron Support Structure Inspection

Type of Inspection – Visual

Initial Compliance: 3000 or 10 years

Recurring Compliance: 500 hours or 5 years

Approximate Labor Time – 3 hours

There is an AD for aileron hinges. If you still have the old style, this would be a logical time to upgrade to the new ones. While the SID focuses on cracks in the hinge, one should also closely inspect for general condition. There should be almost no lateral movement of one half of the hinge to the other. The hinge pin should fit close enough that almost no up-down or fore-aft movement should be detectable.

These hinges should be lubricated frequently. If the plane is stored outdoors, I’d recommend lubricating at least once per month. It just takes a few drops of lube to smooth operation, reduce wear and flash out wear debris. Just keep a can of your favorite spray Silicone or Teflon lubricant in the plane (never WD-40).

 SID 57-53-01 Flap Tracks Corrosion Inspection

Type of Inspection – visual

Initial Compliance: 10 years

Recurring Compliance: 5 years

Approximate Labor Time – 30 mins for inspection only

Exfoliation corrosion is different in appearance than that whitish grey power you’ve probably seen on various skins in your Cessna. Exfoliation often appears to work from the inside of the material, expanding it to a much greater thickness than the original part. It often makes the part look like one of those canned biscuits with all the layers that just open up for you, waiting to be filled with butter and jelly.

SID 71-20-01 Engine Mount Inspection

Type of Inspection – Visual and possible magnetic partical

Initial Compliance: 10,000 hours or 20 years

Recurring Compliance: Engine overhaul Approximate Labor Time – 40 man hours

As you can see from my estimate above, this one has a big expense in labor. The reason is the engine must come off to remove the engine mount. I’d strongly recommend coordinating this with the next time the engine is overhauled to consolidate labor.

If the mount is sent to a shop for any repairs, it’s likely to be returned with a beautiful coat of paint. It is very important that all mating surfaces of the engine mount are stripped down to bare metal. The mount is the primary electrical ground return path for the starter, alternator, and magnetos, so very good contact is needed between the parts. There should also be grounding straps at the rubber mounts on most models. Lack of proper ground return will play havoc with various electrical systems and will get worse over time.

That Does It

I appreciate you all sticking with this. There are a few things I hope you’ve picked up on during this process; these special inspections are worthy of your attention and most aren’t cost prohibitive. Compliance with any -some – most or all is a safety enhancement and good marketing when it’s time to sell the plane. I would recommend you read through all the SIDs that apply to your plane, then speak to your mechanic about implementing as many as you can into the normal routine of an annual inspection.